Deep vein thrombosis (DVT) and pulmonary embolism (PE) constitute major health problems in the United States. It has been estimated that 300,000 to 600,000 hospitalizations a year are attributable to DVT and PE conditions. Venous thromboembolism is also a significant risk in surgical patient populations where preoperative, operative and postoperative immobilization with concomitant loss of venous pump function causes blood stasis.
The use of prophylactic antithrombotic drugs for preventing DVT are known to the art. However, the efficacy of prophylactic administration of anticoagulants and antiplatelet agents has been disputed, and is certainly not absolute. An alternative approach, attractive because of its freedom from hemorrhagic side effects, is the use of physical techniques such as elastic stockings, passive leg exercise, electrical calf stimulation and external pneumatic compression of the legs. Pneumatic compression has been the most studied and appears to be an effective therapeutic technique. For example, the results of a comparison trial between sequential compression and uniform compression are disclosed in an article by E. W. Salzman, et al., entitled Effect of Optimization of Hemodynamics on Fibrinolytic Activity and Antithrombotic Efficacy of External Pneumatic Calf Compression, Annals of Surgery, Vol. 206, No. 5, November (1987), pp. 636-641. Salzman et al. also discloses the lack of commercially available systems for applying external pneumatic compression in an optimized manner, based on blood flow velocity and volumetric flow rate, etc. Antithrombotic modalities based on sequential pneumatic compression are also disclosed in articles by J. A. Caprini, et al., entitled Role of Compression Modalities in a Prophylactic Program for Deep Vein Thrombosis, Seminars in Thrombosis and Hemostasis, Vol. 14, Supp., Thieme Medical Publishers, Inc., pp. 77-87, (1988); and Hull, et al., entitled Effectiveness of Intermittent Pneumatic Leg Compression for Preventing Deep Vein Thrombosis After Total Hip Replacement, Journal of the American Medical Association, Vol 263, No. 17, May, 2, 1990, pp. 2313-2317. Devices for performing sequential compression have also been patented. For example, U.S. Pat. No. 4,396,010 to Arkans, discloses a time-based sequential compression device for simultaneously inflating multiple limb sleeves. Time-based sequential compression devices are also publicly available from The Kendall Company, of Massachusetts. For example, FIG. 1 illustrates an experimentally derived graph of an inflation cycle for a Model 5325 sequential compression device, manufactured by The Kendall Company. It is believed, however, that none of these sequential compression devices and methods provide for optimum blood flow velocity and volumetric flow rate in recumbent patients.
Thus, notwithstanding these attempts to develop compression devices for preventing deep vein thrombosis and pulmonary embolism, there continues to be a need for a gradient sequential compression system which provides a high blood flow velocity and a highly therapeutic prophylactic modality to limbs of a recumbent user.